Refrigerating evaporator



March 15, 1955 E. E. LINDSEY REFRIGERATING EVAPORATOR Filed Jan. 28, 1952 y Q R mww m F .V. w msw m v w w e mm k 1 V. B

United States Patent REFRIGERATING EVAPORATOR Ernest E. Lindsey, Los Angeles, Calif.

Application January 28, 1952, Serial No. 268,605

Claims. (Cl. 62-126) This invention relates to the art of refrigeration.

The invention applies to that type of refrigerating device in which heat passes from the material to be cooled through a heat exchange wall into the expansion chamber of a pressurized liquid refrigerant. The refrigerant may be any one of the standard substances commonly used for such a refrigerant, each of these substances being capable of conversion during the refrigerating cycle from a gaseous state at a relatively low pressure and high temperature to a high pressure liquid.

The refrigerant travels in an endless clrcuit in undergoing a recurring cycle of operations. It is drawn into a compressor as a low pressure, high temperature gas, 1s converted therein into a high pressure, high temperature gas, sent on to a condenser where it is cooled and converted into a high pressure liquid. It is then moved on to a receiver, is usually further cooled and fed from the receiver into the expansion chamber of the machine, usually through a valve controlled by a float on the surface of the liquid in the expansion chamber, is permitted to expand in the expansion chamber and absorb heat from the material to be cooled, through the heat exchange wall of the expansion chamber, and is then, as the last step in the cycle, carried in a conduit from the expansion chamber back to the compressor.

The compressor is alternately started and halted in operation by either a thermostatic temperature control or by a pressure control. In the temperature control, the compressor switch is turned on and off when a thermostat immersed in the refrigerant liquid in the expansion chamber reaches predetermined maximum and minimum temperatures. "In some machines this thermostat is in the material which is being refrigerated. In the pressure type of control, a pressure gauge at the gaseous outlet of the expansion chamber or between the expansion chamber and the compressor, turns off the compressor switch at a predetermined low value and turns it on at a predetermined high value. Thus in either type of control heat exchange continues from the processed material to the refrigerant, as long as there is a temperature differential.

-It is one object of this invention to increase the time rate of thermal flow from the material being refrigerated to the refrigerant. This is done by providing on the refrigerant side of the heat exchange wall a relatively large area of surface contacted by liquid refrigerant as compared to the area of the surface contacted by gaseous refrigerant, all in accordance with this invention. Since for effective gasification and expansion of the refrigerant in the expansion chamber the gasification level of the refrigerant must be relatively low in the expansion cham- 'ber, usually half way or a third way above the intake level, a large area of the refrigerant side of the heat exchange wall is contacted, in present practice, by gaseous refrigerant. For this reason float control of the level is often provided. Since the specific heat and the thermal conductivity of the gaseous refrigerant are both much lower than the same qualities of the liquid refrigerant, it follows that if the area of contact of liquid refrigerant with the heat exchange wall can be increased, the rate of thermal flow will be increased through the heat exchange wall. It is therefore an object of this invention to provide a refrigerating device having a high level of liquid refrigerant against the heat exchange wall, and at the same time maintain the gasification level of the expansion chambet at a low point.

The rate of thermal flow can also be increased by moving the refrigerant, and particularly the liquid particles of the refrigerant more rapidly, over the heat exchange wall. The convection method of heat transfer is thus brought into play. It is therefore another object of this invention to provide for rapid movement of the refrigerant and particularly the liquid particles of the refrigerant over the surface of the heat exchange wall, without unduly raising the gasification level of the expansion chamber.

- Some of the gas bubbles which form in the liquid refrigerant tend to adhere to the walls of the refrigerant expansion chamber. If, however, the liquid refrigerant can be caused to move rapidly over the surface of the heat exchange wall, it is plain that these bubbles will be prevented from thus adhering to the surface of the heat exchange wall, and those bubbles which do adhere thereon will be quickly washed on with the current of the moving liquid refrigerant. As these bubbles have low specific heat and low thermal conductivity, and if allowed to settle on the heat exchange wall, act as heat insulators, there is a definite advantage in keeping them in motion. It is therefore another object of the invention to prevent the formation of stationary gas bubbles adhering to the heat exchange wall.

Since all of the above phenomena result in a faster thermal flow and consequently a more efficient utilization of the heat exchange wall, it follows that the heat exchange wall may be made much smaller in area, with the result that a smaller, more compact device will give the same refrigerating effect quantitatively, as that otherwise requiring a relatively large and expensively constructed device. Small size is especially desirable in midget type confec tion freezers and in individual room air conditioners and similar installations. It is therefore another object of the invention to provide for a given refrigerating duty, a machine of relatively small size and cost.

Since rapidity of refrigeration is desirable in many types of refrigeration equipment, such as beverage coolers, the so-called instant freezers and self-contained air conditioner for hotel rooms, one object of the invention is the provision of a quick acting refrigerating unit.

The returning gaseous refrigerant leaving the expansion chamber on its way back to the compressor usually has a small liquid component in suspension. It is a wet gas. This liquid component has two disadvantages. It represents potential refrigerating capacity which was not utilized in the passage of the refrigerant through the expansion chamber. The liquid component is also diflicult of handling by the compressor, and may cause serious damage to that piece of the refrigerating equipment if present in any appreciable quantity, since the compressor is designed to handle gas and not liquid.

Various devices for eliminating this liquid component of the returning gas have been provided such as finned heat changers in the return conduit and traps from which the separated liquid is conducted to heat exchangers for cooling the condensed and compressed liquid on its way back to the expansion chamber. These devices add to the cost of the equipment. The most desirable condition is that of the discharge of a substantially dry gas from the expansion chamber. It is therefore still another object of the invention to provide a machine so constructed that the returning gas from the expansion chamber to the compressor has a minimum of liquid therein, and to achieve this object by a simple inexpensive arrangement of the expansion chamber, an arrangement which also provides for the accomplishment of the other objects of the invention which have been above recited and explained.

Other objects and advantages of the invention flow from and will be apparent from the nature of the invention, one embodiment of which is shown in the accompanying drawings and described and claimed below.

In the drawings,

Figure 1 is a vertical cross-section of a refrigerating device embodying the invention;

Figure 2 is a horizontal sectional view taken along the line 22 of Figure l; and

Figure 3 is a horizontal sectional view taken along the line 3-3 of Figure 1.

In the equipment shown in the drawings the material to be refrigerated is introduced into a chamber 11 of a hollow cylindrical structure 12. The material may be a liquid beverage to be cooled, a liquid confection to be frozen, air or other gas to be cooled, or any other fluid or solid bodies or particles the temperature of which it is desired to lower. The upper end 13 of the cylindrical structure is shown as open, but it will be understood that a suitable closure will be there provided adapted to the material to be refrigerated and to the purpose of the refrigerating process. While a closure 14 with a discharge opening 15 is shown at the lower end of the cylindrical structure, such as may be used in a confection freezer, the lower end of the chamber 11 may be provided with any kind of support for the material in the chamber, any kind of outlet, and with discharge conduit connections appropriate to the kind of refrigerating operation for which the equipment is designed.

In the particular construction of cylinder selected to illustrate the invention, the built up cylinder wall comprises an inner heat exchange wall 16 in the form of a hollow cylinder, an outside hollow cylinder 17, end flat rings 18 and 19, and an intermediate hollow cylinder wall 20, spaced from the heat exchange wall by upper and lower disk rings 21 and 22. The chamber between cylinders 17 and is filled with thermal insulation 23. Between cylinders 16 and 20 is an expansion chamber 24 into the lower end of which the refrigerant in liquid form enters through a pipe 25 and from the upper end of which the refrigerant leaves in gaseous form through a pipe 26.

The pipes 25 and 26 lead to the compressor, condenser and cooling devices, which are not shown since they may be of any of the conventional types of liquid vaporizing refrigerating equipment.

The expansion chamber 24 is divided into two compartments from a level just above the intake pipe 25 to the top of the expansion chamber. To provide these two compartments designated 27 and 28, a cylindrical wall 29 is secured to a ring flange 30, and the wall 29 and flange 30 are mounted in the expansion chamber on legs 40 which rest on ring 22. The flange 30 fits snugly within cylinder wall 20. The wall 29 is maintained in relatively closely spaced relation to the heat exchange wall 16 by a plurality of suitably disposed dimples formed in the sheet metal of the wall 29. The wall 29 is so related to walls 16 and 20 that the radial dimension of the compartment 27 is substantially greater than the radial dimension of the compartment 28, as for example in the ratio of four or five to one. The volumes of the two compartments are therefore similarly related.

The flange 30 is provided with a plurality of perforations 31, as for example four. These holes offer a restricted communicating connection between compartments 27 and 28 through the lower end of the expansion chamber 24. It will be understood that the expansion chamber comprises both compartments 27 and 28 as well as the small lower end of the expansion chamber below these two chamber compartments. The operation of the device is better with a restricted communicating connection between the two compartments at their lower ends, but the perforations 31 may be increased in size and number, or the flanges 30 omitted altogether and the cylinder 29 supported directly on legs 40, without destroying the manner of operation of the invention, which will be described below.

The wall 29 terminates at its upper end a short distance below the disk 21, providing an annular passageway 32. A cylindrical baflle plate 33 is secured to the disk 21 and extends downwardly outside and closely adjacent the wall 29 a suflicient distance to block direct straight line movement of fluids from the passageway 32 to the pipe 26. From the lower cylindrical edge of the baffle plate 33 is suspended a cylindrical open work veil 34 which may suitably be made of mesh Wire screen cloth. This veil extends well down from the baffle 33 to the flange 30, as for example halfway. The bafile 33 provides narrow annular passageway 36 with fluid tight side walls, and the veil 34 provides a continuation 37 of this passageway 36 with an outer fluid pervious wall.

The refrigerant handling devices of the machine are adjusted to hold the liquid refrigerant at a stabilized level 38 when no material is in chamber 11. This level is usually from /3 to /2 of the length of the expansion chamber above its lower end. The liquid refrigerant is under idle conditions at the same level in both compartments 27 and 28, the perforations 31 permitting the liquid in both compartments to seek the same level. The portion of the expansion chamber above the liquid is filled with gaseous refrigerant.

When a relatively warm material is introduced into chamber 11, heat flows through heat exchange wall 16 mto the expansion chamber, and gas bubbles form in the liquid in the lower end of compartment 28, but not appreciably in the lower end of compartment 27, since the wall 29 shields compartment 27 from a direct flow of heat units from the material in chamber 11. The liquid column between walls 16 and 29 then tends to rise above liquid level 38 due to the lightening effect of the bubbles forming therein. The mixed liquid and gas rises in the manner of a gas lift liquid pump and flows over the upper edge of cylinder 29 through passage 32, dropping down into passage 36, as indicated by the solid line arrows 41. When it reaches the lower edge of baffle 33, the gas component of the mixture flows outwardly through the meshes of the veil 34, rises in compartment 27 and passes into pipe 26 as a dry gas as indicated by the broken line arrows 42. The liquid component drops into the lower end of compartment 27 where it strikes the well of liquid at level 38 as indicated by the liquid drops 43. While this level tends to remain stationary under the usual operative conditions, a float in compartment 27 may be provided for the operation of a valve in pipe 25 to automatically maintain this level at a constant position.

By this novel arrangement of walls to provide two compartrnents in the expansion chamber, and the further provision of the baffle plate and veil, an extended surface of thermal flow from the material being refrigerated into the liquid refrigerant is provided, and the refrigerant having a large liquid component is caused to move rapidly along this extended surface washing the gas bubbles there from, the liquid component being recirculated, and the gas bubbles being drawn off into pipe 26 as a dry gas.

I claim:

1. In a refrigerating device of the liquid-gas expansion type, the combination of: walls providing an enclosed expansion chamber; an inlet conduit opening into said chamber; an outlet conduit opening into said chamber at an upper level; a dividing wall in said chamber arranged to provide two vertically extending compartments therein, the two campartments having connecting passages at their upper and lower ends, a first of said compartments being bounded in part by the heat exchange wall of the expansion chamber, and the port of the outlet conduit leading from the second compartment; a vertically arranged bafile plate mounted in the second chamber opposite the upper connecting passage so as to present a vertical wall to substantially all the fluid flowing through said passage, the baffle plate extending downward below the upper level of the upper connecting passage; and a multiple apertured open-work bafile wall mounted directly below the baffle p ate.

2. In a refrigerating device of the liquid-gas expansion type, the combination of: walls providing an enclosed expansion chamber; an inlet conduit opening into said chamber; an outlet conduit opening into said chamber at an upper level; a dividing wall in said chamber arranged to provide two vertically extending compartments therein, the two compartments having connecting passages at their upper and lower ends, a first of said compartments being bounded in part by the heat exchange wall of the expansion chamber, and the port of the outlet conduit leading from the second compartment; and a vertically arranged diversion wall mounted in the flow path of substantially all the refrigerant from the upper connecting passage to the outlet port, said diversion wall being disposed to direct the refrigerant downwardly, and being characterized by a large number of small apertures, distributed over at least the lower portion of said diversion wall.

3. The combination defined in claim 1 in which the bafile plate has a substantially fluid tight joint with the walls of the second compartment except at the lower edge of the bafile plate, and projects substantially below the upper connecting passage and is closely spaced laterally from the dividing wall, and the open work multiple apertured baflle wall is a downward continuation of the baflle plate and similarly spaced from the dividing wall.

4. In a refrigerating device of the liquid-gas expansion type, the combination of a heat-exchange inner wall surrounding a chamber for holding the material to be refrigerated; an outer wall and an intermediate wall surrounding the inner wall; thermal insulation between the outer and intermediate walls, the intermediate and inner wall enclosing a refrigerant expansion chamber; a dividing wall in the refrigerant expansion chamber closely spaced from the heat exchange inner walland extending from a level adjacent the bottom of said chamber to a level adjacent the top of said chamber providing a downwardly and upwardly open first compartment of said expansion chamber between the inner wall and the dividing wall and a second upwardlyopen compartment between the dividing wall and the intermediate wall, said second compartment being of a volume at least twice as great as the volume of the first compartment; a closure with a relatively small opening at the bottom of the second compartment, the intermediate wall being formed with an inlet port below said closure, and an outlet port at the upper end of said second compartment; 21 solid bafiie plate surrounding the upper end of the dividing wall and extending from the top of the expansion chamber to a level substantially below the top of the dividing plate and closely spaced from the dividing wall; and an open work bafile wall extending downward from the lower end of the baflie plate and similarly star rounding the dividing wall and closely spaced therefrom.

5. The combination defined in claim 4, in which the said inner, outer and intermediate walls are in the form of concentric hollow cylinders with end closures, the dividing wall, baffle plate and baflle wall are in the form of concentric hollow cylinders concentrically related to said inner, outer and intermediate walls, and the said closure is an annular ring.

References Cited in the file of this patent UNITED STATES PATENTS 1,976,101 Ziegler Oct. 9, 1934 2,519,844 Mojonnier Aug. 22, 1950 FOREIGN PATENTS 622,452 Great Britain May 2, 1949 

